| Forest conversion is one of the common land use patterns.Soil microorganisms are important driving factors of biogeochemical cycle in terrestrial ecosystems,and their characteristics are often used as important biological indicators of soil ecosystem productivity.In order to reveal the effects of forest conversion on soil ecosystem productivity in the mountainous area of southern Anhui,in this study,the secondary forests of Pinus Massoniana（PM）,and Pinus Elliottii（PE）and Cunninghamia Lanceolata（CL）plantations converted from the secondary forests of PM were sampled in investigation of soil physicochemical property and soil microbiology features.By analysis of soil physical and chemical properties,soil microbial biomass,soil enzyme activity and the correlation between soil bacterial community structure and diversity,it can reveal the key environmental factors controlling soil bacterial community structure in conversion of forest types,in order to provide theoretical and scientific basis for the sustainable management of forest soil ecosystem.The main results of this study are as follows.（1）Forest conversion significantly changed soil physicochemical property.After PM was converted into PE,NO3--N and AP contents in 0-10-cm soil layer decreased significantly.Soil pH increased significantly in 0-10-cm,10-30-cm and 30-50-cm layers,while soil EC decreased significantly.NH4+-N content was the highest,NO3--N content was the lowest among the three forest types.After PM conversion into CL,the contents of SOC and AP in 0-10-cm soil layer decreased significantly,SWC increased significantly,and SOC content and EC decreased significantly.SWC was the highest among the three forest types,while SOC,TN,TP and NH4+-N contents were the lowest.In the three forest types,except for soil pH of PM and CL and SWC of PM,the other soil physicochemical property decreased with the deepening of soil layer.（2）Forest conversion did not significantly change soil microbial biomass.The content of MBC did not change significantly in the three soil layers after PM was converted into PE and CL.The content of MBC in PE was the highest in 0-10-cm and30-50-cm soil layers of the three forest types.MBN content did not change significantly in the three soil layers after PM was converted into CL,but increased significantly after PM was converted into PE,which was the highest among the three forest types.The content of MBC and MBN in the three forest types decreased with the deepening of soil layer vertically.（3）Forest conversion significantly changed soil enzyme activities.Soil acid phosphatase and soil sucrase activities decreased in the three soil layers after PM was converted to PE and CL,and ordered in PM>PE>CL for all three forest types.The trend of soil catalase activity was different in the three soil layers after forest conversion.Soil urease activity increased significantly in the three soil layers after PM was converted to PE and was significantly higher than that of CL.The activities of four soil enzymes decreased with soil depth.（4）Forest conversion significantly changed soil bacterial diversity.The trends of the Chao1 index,Observed＿species index,Shannon index and Simpson index of soil bacteria in 0-10 cm and 10-30 cm layers of three forest types were PE>CL>PM.Theαdiversity index of bacterial in 0-10 cm soil layer was higher than that in 10-30 cm soil layer.Principal coordinate analysis showed that the differences among the three forest types were significantly greater than the differences within the groups,and the soil layers between 0-10 cm and 10-30 cm were significantly different.（5）Forest conversion significantly changed soil bacterial community structure.In 0-10 cm soil layer:at the phylum level,the three dominant phyla were Acidobacteria,Proteobacteria and Actinobacteria,among which the relative abundance of PE was the lowest,and that of CL was the lowest.At the genus level,the three dominant genera were Subgroup＿2＿unclassified,Acidobacteriales＿unclassified and Elsterales＿unclassified,among which PE was the lowest in relative abundance.In the10-30 cm soil layer:at the phylum level,the three dominant bacteria phyla were Acidobacteria,Proteobacteria and Chloroflexi,and the relative abundance of Acidobacteria and Chloroflexi in PE was the lowest.At the genus level,Subgroup＿2＿unclassified,Acidobacteriales＿unclassified and Elsterales＿unclassified were still the dominants of the three forest types.However,the second most dominant genera of PM and CL was AD3＿unclassified.（6）According to Mantel analysis of soil environmental factors and soil bacterial community,Soil EC was the most important environmental factor affecting soil bacterial community,followed by soil pH and NO3--N.Meanwhile,SOC,TN,AP,MBC,MBN,S-CAT,S-SC and S-URE also significantly affected soil bacterial community structure in this region.The comprehensive analysis showed that,from the perspective of microbial characteristics,the transformation from PM to PE was more beneficial to the development of soil bacterial community and soil nutrient maintenance,and to the restoration and sustainable management of soil ecosystem in mountain area in southern Anhui. |
